This invention relates to franking mail items in which a postage indicium is printed on the mail item to provide evidence that accounting for a postage charge in respect of the mail item has been effected.
Postage meters are well known in which a user can input, by means of a keyboard, a desired postage charge for a mail item and the postage meter then carries out accounting functions in respect of the required postage charge and prints a postage indicium on the mail item. The postage indicium includes data indicative of the postage charge applied whereby post office personnel can check that the correct postage charge has been applied taking into account the weight, class of postal service and destination of the item. Although the ink used to print the postage indicium is of a specified colour and quality which is not available for use in equipment other than postage meters, with the advent of photocopiers capable of copying coloured imprints it is relatively easy to make copies of printed postage indicia which are reproduced with sufficient accuracy as to present a printed image which appears to be authentic. Accordingly by the use of a colour photocopier mail items bearing what appears to be a genuinely printed postage indicium can be created. However, it will be appreciated that copies of postage indicia on mail items result in fraud on the postal authority because no accounting or payment has been made in respect of the copies of postage indicia. Copying of postage indicia could result in significant financial loss to a postal authority and particularly if postage indicia indicating high values of postage charge are copied. Accordingly it is of significant interest to postal authorities to prevent copying of postage indicia.